On Fri, Mar 4, 2016 at 5:17 AM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> On Thu, Mar 03, 2016 at 09:16:33AM +0100, Miklos Szeredi wrote:
>> My plan was to introduce a file_dentry() helper that MUST be used by
>> filesystems to get the dentry from the file and that makes sure it's
>> the right one (check against file_inode()). If not, then we could
>> call into overlayfs to return the right one, similar to
>> ->d_select_inode(), except we want to have a dentry and we want to
>> have *a particular dentry* matching file_inode() (the file could have
>> been copied up in the mean time).
>
> Something like the following (untested, against overlayfs-next.git)
>
> Thanks,
> Miklos
>
> ---
> fs/nfs/dir.c | 6 +++---
> fs/nfs/inode.c | 2 +-
> fs/nfs/nfs4file.c | 4 ++--
> fs/open.c | 11 +++++++++++
> fs/overlayfs/super.c | 16 ++++++++++++++++
> include/linux/dcache.h | 1 +
> include/linux/fs.h | 2 ++
> 7 files changed, 36 insertions(+), 6 deletions(-)
>
> --- a/fs/nfs/dir.c
> +++ b/fs/nfs/dir.c
> @@ -377,7 +377,7 @@ int nfs_readdir_xdr_filler(struct page *
> again:
> timestamp = jiffies;
> gencount = nfs_inc_attr_generation_counter();
> - error = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred, entry->cookie, pages,
> + error = NFS_PROTO(inode)->readdir(file_dentry(file), cred, entry->cookie, pages,
> NFS_SERVER(inode)->dtsize, desc->plus);
> if (error < 0) {
> /* We requested READDIRPLUS, but the server doesn't grok it */
> @@ -560,7 +560,7 @@ int nfs_readdir_page_filler(nfs_readdir_
> count++;
>
> if (desc->plus != 0)
> - nfs_prime_dcache(desc->file->f_path.dentry, entry);
> + nfs_prime_dcache(file_dentry(desc->file), entry);
>
> status = nfs_readdir_add_to_array(entry, page);
> if (status != 0)
> @@ -864,7 +864,7 @@ static bool nfs_dir_mapping_need_revalid
> */
> static int nfs_readdir(struct file *file, struct dir_context *ctx)
> {
> - struct dentry *dentry = file->f_path.dentry;
> + struct dentry *dentry = file_dentry(file);
> struct inode *inode = d_inode(dentry);
> nfs_readdir_descriptor_t my_desc,
> *desc = &my_desc;
> --- a/fs/nfs/inode.c
> +++ b/fs/nfs/inode.c
> @@ -940,7 +940,7 @@ int nfs_open(struct inode *inode, struct
> {
> struct nfs_open_context *ctx;
>
> - ctx = alloc_nfs_open_context(filp->f_path.dentry, filp->f_mode);
> + ctx = alloc_nfs_open_context(file_dentry(filp), filp->f_mode);
> if (IS_ERR(ctx))
> return PTR_ERR(ctx);
> nfs_file_set_open_context(filp, ctx);
> --- a/fs/nfs/nfs4file.c
> +++ b/fs/nfs/nfs4file.c
> @@ -26,7 +26,7 @@ static int
> nfs4_file_open(struct inode *inode, struct file *filp)
> {
> struct nfs_open_context *ctx;
> - struct dentry *dentry = filp->f_path.dentry;
> + struct dentry *dentry = file_dentry(filp);
> struct dentry *parent = NULL;
> struct inode *dir;
> unsigned openflags = filp->f_flags;
> @@ -57,7 +57,7 @@ nfs4_file_open(struct inode *inode, stru
> parent = dget_parent(dentry);
> dir = d_inode(parent);
>
> - ctx = alloc_nfs_open_context(filp->f_path.dentry, filp->f_mode);
> + ctx = alloc_nfs_open_context(file_dentry(filp), filp->f_mode);
> err = PTR_ERR(ctx);
> if (IS_ERR(ctx))
> goto out;
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1234,6 +1234,8 @@ static inline struct inode *file_inode(c
> return f->f_inode;
> }
>
> +extern struct dentry *file_dentry(const struct file *file);
> +
> static inline int locks_lock_file_wait(struct file *filp, struct file_lock *fl)
> {
> return locks_lock_inode_wait(file_inode(filp), fl);
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -831,6 +831,17 @@ char *file_path(struct file *filp, char
> }
> EXPORT_SYMBOL(file_path);
>
> +struct dentry *file_dentry(const struct file *file)
> +{
> + struct dentry *dentry = file->f_path.dentry;
> +
> + if (d_inode(dentry) == file_inode(file))
> + return dentry;
> + else
> + return dentry->d_op->d_select_dentry(dentry, file_inode(file));
> +}
> +EXPORT_SYMBOL(file_dentry);
> +
> /**
> * vfs_open - open the file at the given path
> * @path: path to open
> --- a/fs/overlayfs/super.c
> +++ b/fs/overlayfs/super.c
> @@ -336,14 +336,30 @@ static int ovl_dentry_weak_revalidate(st
> return ret;
> }
>
> +static struct dentry *ovl_d_select_dentry(struct dentry *dentry,
> + struct inode *inode)
> +{
> + struct ovl_entry *oe = dentry->d_fsdata;
> + struct dentry *realentry = ovl_upperdentry_dereference(oe);
> +
> + if (realentry && inode == d_inode(realentry))
> + return realentry;
> + realentry = __ovl_dentry_lower(oe);
> + if (realentry && inode == d_inode(realentry))
> + return realentry;
> + BUG();
> +}
> +
> static const struct dentry_operations ovl_dentry_operations = {
> .d_release = ovl_dentry_release,
> .d_select_inode = ovl_d_select_inode,
> + .d_select_dentry = ovl_d_select_dentry,
> };
>
> static const struct dentry_operations ovl_reval_dentry_operations = {
> .d_release = ovl_dentry_release,
> .d_select_inode = ovl_d_select_inode,
> + .d_select_dentry = ovl_d_select_dentry,
> .d_revalidate = ovl_dentry_revalidate,
> .d_weak_revalidate = ovl_dentry_weak_revalidate,
> };
> --- a/include/linux/dcache.h
> +++ b/include/linux/dcache.h
> @@ -161,6 +161,7 @@ struct dentry_operations {
> struct vfsmount *(*d_automount)(struct path *);
> int (*d_manage)(struct dentry *, bool);
> struct inode *(*d_select_inode)(struct dentry *, unsigned);
> + struct dentry *(*d_select_dentry)(struct dentry *, struct inode *);
> } ____cacheline_aligned;
>
> /*
Thanks Miklos! That looks reasonable, assuming it tests out correctly.
Cheers
Trond
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